Scientists Unsure if Methane at Mars Points to Biology or Geology

A trio of research teams independently probing the Martian atmosphere for signs of methane have found it, a combined discovery that opens the door for a host of theories as to how the colorless, odorless gas got there. Among the most tantalizing, if not very likely, of scenarios, scientists say, is the possibility that the Mars methane could be the byproduct of some form of microbial life. But a safer bet, they say, centers on the geology of Mars, including anything from volcanic activity to long-ago impacts of methane-carrying comets.